Heat Exchanger Technology
Background
In a plate heat exchanger (PHE) two mediums (i.e., air, gas, liquid) flow in counter or cross flow arrangement to each other. The mediums/flows are separated from each other by corrugated plates. The plate corrugation (form, depth and angles), plate size and number of plates varies depending on the application, the medium, the required flow and the required heat transfer capacity. Vacuum brazed plate heat exchangers (CBE) are made from pressed stainless steel plates which are stacked together. The stacked plate package is carefully brazed together with copper or nickel solder at high temperature and under vacuum.
During the vacuum brazing process brazed contact points are created between each plate to provide superior mechanical strength. The result, CBE, Compact Brazed Exchangers, have a large heat transfer surface, are extremely efficient, and are at the same time compact and light. Normally a CBE is 10 – 20% in weight and volume of the equivalent shell-and-tube exchanger. Even at low inlet temperature difference between the mediums CBE can fulfil the most demanding heat transfer duties. The innumerable brazing points make BPHE the perfect choice for high pressures or temperatures.
Now: The best solution regardless of application
Over the past fifteen years, brazed plate heat exchangers (CBE), have developed into the standard solution for symmetrical liquid-to-liquid heat transfer , due to their compact design and high performance. Airec has taken their development to the next level.
By optimizing the plate design and corrugation, while keeping all of the benefits of the traditional CBE, our products can also be used for applications with larger volume flows, lower pressure drops or completely asymmetrical flows. (i.e. the volumes and/or the pressures of the two flows through the heat exchanger are different.)
The Extremes
Inlet and outlet open to minimise pressure drop. Unique plate pattern designed for low pressure drop. Hundreds of contact points between each plate provide high mechanical strength.
Brazed Gas-to-Gas
Inlet and outlet through round connections. Unique plate pattern designed for extremely high heat transfer. Thousands of contact points between each plate provide superior mechanical strength.
Brazed Liquid-to-Liquid
The Asymmetrical Design
Asymmetrical Design for Asymmetrical applications
Most applications for heat transfer require a heat exchanger that can effectively handle two flows with completely different volumes. Water-to-Air Heat transfer is just one of numerous heat transfer applications with different volume flows.
In standard CBE:s (Compact Brazed Exchanger) the two heat exchanger sides are identical, which make them unsuitable for all asymmetrical applications
Our brazed exchangers, (Cross, Compact and BGG) still have the significant advantages of high efficiency, compactness, mechanical strength and gas tight design. But as the two sides in the heat exchangers are internally different the Compact Brazed Exchanger range is the obvious solution for asymmetrical applications.
Cross
Cross flow arrangement. Two different plate types with identical dimensions are stacked together alternately creating a large volume flow channel (low pressure) and alternately a small volume flow channel (high pressure).
The high pressure side has round connections and high thermal efficiency so it can handle a “small” volume flow like a liquid or a high pressure gas.
The low pressure side has completely open inlets / outlets and a plate design to allow maximum volume flow with low pressure drop.
Compact
Counter flow arrangement for maximum heat transfer and efficiency.
The plates are stacked together alternately creating a large volume flow channel (side B with low pressure drop) and alternately a smaller volume flow channel (side A with higher pressure drop).
All connections are integrated in the heat exchanger. No outside housing or casing is required.
Compact is complete with condensate connection so condensation in the gas medium in side B easily can drain out from the heat exchanger.
Compact has an even higher thermal efficiency than AirCross due to its compact design and large heat transfer surface.
Often can a thermal efficiency for the gas side above 95% be reached.
All outside surfaces are effectively cooled by
streaming side A medium as the medium in side A normally is a cooler liquid compared to the hot gas medium in side B.
The water cooling jacket minimizes energy losses, reduces thermal stress and eliminates the need of insulation and high temperature shields.
Normally is the surface temperature so low as 20°C higher than the water temperature.
The High Efficient Design
The whole surface in Cross, Compact and BGG is part of the primary heat exchanger surface. The plate corrugation is specially designed for asymmetrical applications and to maximize efficiency with minimum pressure drop.
Traditionally fin-tube heat exchangers are used in asymmetrical applications, such as oil-to-air coolers. Our Compact Brazed Exchangers have 10 – 50 times larger primary heat transfer surface for equal volume than the fin-tube design and offers therefore much higher efficiency.
The fin-tube design only has advantages for applications where no temperature efficiency is required on the larger flow side, for instance the cooling airflow in different coolers.
The primary heat transfer surface is the surface that separates the two flows from each other and actively transfers heat. The fins are secondary heat transfer surface, as they do not transfer energy directly from the hot flow to the cold flow.
The Asymmetrical Design
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